“LCR” has become a buzz word over the past 5 years or so. As with many other fads, it is based on an old concept, then divorced from its original purpose.
The original purpose was much like M/S recording (mid-side), which is described on Wikipedia here: https://en.wikipedia.org/wiki/Joint_(audio_engineering)#M.2FS_stereo_coding
A more detailed description: http://www.uaudio.com/blog/mid-side-mic-recording/
and an “advanced” and detailed article about using the technique creatively here: http://www.soundonsound.com/sos/apr12/articles/reaper-0412.htm
The basic idea is that by separating the “side” information from the “mid” information, the stereo width can be controlled / adjusted in post production.
Note that although this technique involves 3 audio channels, they are not 3 independent audio channels. You can’t for example record a guitar, a vocal and a piano on a 2 channel recording and then isolate each sound in post production. (Well actually, it is possible to get pretty close to that using FFT processing, but the sound quality takes a bit of a bashing. See rjh-stereo-tool.ny here: https://forum.audacityteam.org/t/karaoke-rotation-panning-more/30112/1).
The more recent fad is the idea that panning only hard left, hard right and dead centre, gives a better mix (in my opinion it sounds dreadful 
especially on headphones).